Effects of artificial and natural baroreceptor stimulation on nociceptive responding and pain.

The arterial baroreflex may mediate hypertensive hypoalgesia. Carotid baroreceptors can be artificially stimulated by neck suction and inhibited by compression. Effects of brief neck suction and compression on nociceptive responding and pain were studied in 25 normotensive adults. The sural nerve was electrocutaneously stimulated at threshold intensity during systole or diastole combined with neck suction, neck compression, or no pressure. Nociceptive responding was indexed by electromyographic activity elicited in the biceps femoris. Participants rated the intensity of sural stimulation. Although artificial baroreceptor stimulation (suction) did not affect nociceptive responding, baroreceptor inhibition (compression) reduced pain ratings. In contrast, natural baroreceptor stimulation during systole reduced nociceptive responding compared to diastole, but did not affect pain ratings. The data provide partial support for baroreflex modulation of pain.